I have done a similar conversion on my 1992 Westfield SE. One thing to add is that if upgrading the power of the lights/ increasing current draw you may want to upgrade the light switches on the dash. When using my SE as my only car for a year with lots of night driving I found the old plastic rocker switches would gradually degrade. This was due to the heat build up from the current slightly softening the plastic in the switch. Over time the result was that you sometimes got intermitent contact and had to move the switch several times for the light to work. If you hit a hard bump like a pot hole it could cause the lights to go out !! I once had to use the hazards to see where I was going until I stopped which was a bit hairy. It should be noted I was using the lights a lot. My old MOTs show I did 28,000 miles in the first two years on the road. Newer Westfield switches may be better. I started replacing the switch at regular intervals. I have been told one better method is to install a relay to operate the main/full beam, though I'm not sure how road legal that approach is.
Hi the fitting of a relay is a must for you - there is no legal issue here - all modern cars use relays. Relays split the lights circuit into 2 parts - the low current side ( the switch and dash wiring ) and the high current side - this goes from the battery to the lights directly.
